The stress and annoyance of rush hour traffic on a clogged highway can give you a figurative heart attack or stroke. Clogs in the arteries of your circulatory system, your body’s highway, can give you a real heart attack or stroke. This condition—atherosclerosis—is commonly treated with bypass surgery, during which a blood vessel from another part of the body such as the leg is used to redirect blood flow around the blocked area. However, what if suitable donor vessels cannot be found? A technique currently being developed in animal models to address this problem involves implanting a plastic tube into the body and triggering the host cells to coat the tube with tissue. After removal from the body, the plastic tube is separated from the biological coating/tube, which is used as a “foreign body vascular graft.” These grafts, however, can fail under high blood flow because of poor mechanical strength. To begin to address this weakness, Stickler et al. developed a method to cyclically stretch the developing foreign body grafts in vivo to increase their mechanical strength before use in bypass surgery.

Stickler et al. designed a construct composed of a plastic tube with an enclosed inflatable bladder. This construct was implanted into the abdominal wall of a sheep with an external port allowing the bladder to be inflated and deflated, resulting in cyclical stretching of the developing vascular graft. After 8 days of in vivoculture, the cyclically stretched grafts were denser, better aligned, and twice as strong as unstretched controls. These stretched grafts, however, still did not have the mechanical strength to function completely as a bypass blood vessel. Nonetheless, these findings demonstrate that cyclical loading can improve the mechanical strength of foreign body vascular grafts. With further research and development, these grafts may represent an additional option for bypass surgery and the treatment of atherosclerosis.